Göran Ekström's main research interest is global earthquake seismology. This includes the detailed study of individual earthquake ruptures, and the relationship between seismicity and the large scale tectonic deformation of the crust and mantle over geolo

News items

Seismologist Won-Young Kim heard the first reports of the Sept. 11, 2001, attacks on the World Trade Center as he drove to his job at Columbia University's Lamont-Doherty Earth Observatory. From his office on the west bank of the Hudson River, 21 miles north of lower Manhattan, Kim runs a network of seismic instruments that monitors the U.S. Northeast for earthquakes. When he got to work, everyone was glued to the radio. Soon, he was inundated by calls from government officials and reporters. In the initial chaos, it was unclear exactly what had hit, and when; had the seismographs picked up anything?

A new study carried out on the floor of Pacific Ocean provides the most detailed view yet of how the earth’s mantle flows beneath the ocean’s tectonic plates. The findings, published in the journal Nature, appear to upend a common belief that the strongest deformation in the mantle is controlled by large-scale movement of the plates. Instead, the highest resolution imaging yet reveals smaller-scale processes at work that have more powerful effects.

Last Thursday, thousands of people from southern New Jersey to Long Island and coastal Connecticut felt the earth tremble. Between 1:20 pm and 2:40 pm, dishes, desks and buildings shook for up to 20 seconds—in some locations, several times. With everyone thinking earthquake, Twitter and Facebook lit up; news reporters scrambled; calls poured into police, the U.S. Geological Survey, and Columbia University’s Lamont-Doherty Earth Observatory, which maintains the region’s network of 50-some seismographic stations.

Over the last six years, seismologists Göran Ekström and Colin Stark have been perfecting a technique for picking out the seismic signature of large landslides from the stream of seismic data from earthquakes and other activity around the world. The details they are able to extract could one day help governments sound tsunami warnings, help rescuers find landslide-struck villages faster, and warn of risks such as landslide-dammed rivers that could soon burst through.

Most earthquakes erupt suddenly from faults near Earth’s surface, and the big ones can topple cities. But miles below, rocks heated to the consistency of wax moving over thousands to millions of years may be the driving force behind some of these events.

A new study in the journal Geology is the latest to tie a string of unusual earthquakes, in this case, in central Oklahoma, to the injection of wastewater deep underground. Researchers now say that the magnitude 5.7 earthquake near Prague, Okla., on Nov. 6, 2011, may also be the largest ever linked to wastewater injection. Felt as far away as Milwaukee, more than 800 miles away, the quake—the biggest ever recorded in Oklahoma--destroyed 14 homes, buckled a federal highway and left two people injured. Small earthquakes continue to be recorded in the area.

During Hurricane Sandy the seas rose a record 14-feet in lower Manhattan. Water flooded city streets, subways, tunnels and even sewage treatment plants. It is unclear how much sewage may have been released as plants lost power or were forced to divert untreated wastewater into the Hudson River.

This spring, a Swedish scientist sparked international concern with a journal article saying that radioactive particles detected in 2010 showed North Korea had set off at least two small nuclear blasts--possibly in experiments designed to boost the yields of much larger bombs. Shortly after, the pot was stirred with separate claims that some intelligence agencies suspected the detonations were done in cooperation with Iran. Now, a new paper says the tests likely never took place—or that if they did, they were too tiny to have any military significance. The new report, by seismologists at Columbia University’s Lamont-Doherty Earth Observatory, will be published later this month in the journal Science & Global Security, where the earlier paper also appeared.

Lamont-Doherty Earth Observatory director G. Michael Purdy has been named Columbia University’s executive vice president for research. Taking over as interim director of the observatory is associate director Arthur Lerner-Lam. The moves, effective Feb. 1, were announced by Columbia president Lee Bollinger and Earth Institute director Jeffrey Sachs in emails to staff Jan. 19.

Dr. John Ertle “Jack” Oliver, a geophysicist whose research helped revolutionize our understanding of the basic forces shaping the planet, died peacefully at his home in Ithaca, N.Y., on Wednesday, Jan. 5, 2011. He was 87.

In a research career spanning more than four decades, Paul Richards, a seismologist at Lamont-Doherty Earth Observatory, has helped uncover Earth’s inner structure and advanced techniques for detecting nuclear explosions to ensure that bans on nuclear testing can be enforced. Richards will receive the Seismological Society of America’s Harry Fielding Reid medal at its annual luncheon on Wednesday, April 21.

This week U.S. and Haitian scientists will start a 20-day research cruise off Haiti to address urgent questions about the workings of the great Jan. 12 earthquake, and the possibility of continuing threats. They hope to gather sonar images, sediments and other evidence from the seafloor that might reveal hidden structures...

The earthquake that struck Haiti took place along what is called a strike-slip fault—a place where tectonic plates on each side of a fault line are moving horizontally in opposite directions, like hands rubbing together. When these plates lock together, stress builds; eventually they slip; and this produces shaking.

That rumbling you feel is not necessarily a passing subway. New York City and the surrounding region gets a surprising number of small earthquakes, and a 2008 study from the region’s network of seismographs, run by Lamont-Doherty Earth Observatory, suggests that the risk of a damaging one is not negligible. This week, the federal government announced a major upgrade to that network.

Ordinarily, losing almost all of one's instruments would be considered a severe setback to any scientist. But when Maya Tolstoy, a marine geophysicist at the Lamont-Doherty Earth Observatory and the Earth Institute at Columbia University, recently learned that two-thirds of the seismometers she placed on the floor of the Pacific Ocean were trapped more than 8,000 feet (2500 meters) underwater, it turned out to be an extremely good sign.

Seismologists at Columbia University and Harvard University have found a new indicator that the Earth is warming: "glacial earthquakes" caused when the rivers of ice lurch unexpectedly and produce temblors as strong as magnitude 5.1 on the moment-magnitude scale, which is similar to the Richter scale. Glacial earthquakes in Greenland, the researchers found, are most common in July and August, and have more than doubled in number since 2002.

When the sea floor off the coast of Sumatra split on the morning of December 26, 2004, it took days to measure the full extent of the rupture. Recently, researchers at Columbia University's Lamont-Doherty Earth Observatory analyzed recordings of the underwater sound produced by the magnitude 9.3 earthquake.

Finding the epicenter of earthquakes has not changed in principle since the 1930s -- after closely examining seismograms from different widely-spaced listening stations, researchers decide on the arrival times of various seismic waves and calculate an approximation. In practice this can result in errors of several miles

Researchers have found an important new application for seismic reflection data, commonly used to image geological structures and explore for oil and gas. Recently published in the journal Nature, new use of reflection data may prove crucial to understanding the potential for mega earthquakes.